Pollution, Water

Sources of Pollution

There are many sources of water pollution, such as city sewage, also known as sanitary sewage or domestic sewage, which refers to wastewater from households. This water contains a wide variety of dissolved and suspended impurities such as organic materials and plant nutrients, and human waste. It contains inorganic products such as synthetic detergents containing phosphates, which affect the health of all forms of life in water. Most cities do not have adequate facilities to treat wastewater and much of it is discharged into water bodies.

Bacterial contamination of surface water from sewage caused serious health problems in major cities in Europe and North America in the mid-19th century. Cities built sewer networks to route domestic waste downstream of drinking water intakes to prevent contamination of the drinking water. These sewage networks and waste treatment facilities expanded rapidly in the developed world. In the developing world, where governments sometimes lack financial resources to expand sewage and water infrastructure, outbreaks of waterborne diseases like cholera still occur.

Industrial waste or effluents, usually containing specific and readily identifiable chemical compounds, are another source of water pollution. Many plants (e.g., paper mills, tanneries, sugar mills, distilleries, and thermal power stations) generating these effluents do not have adequate treatment facilities because these small-scale industries cannot afford enormous investments in pollution control equipment. Major industries have treatment facilities for industrial effluents, yet enough small-scale operations pollute water to counter measures taken by major industries.

Agricultural runoff is another source of water pollution. Intensive cultivation of crops usually involves chemicals (nitrates, phosphates) and pesticides (such as DDT) and water from these fields containing fertilizers and pesticides not only drains into rivers or lakes, but also seeps into groundwater in a process known as leaching. Scientists also believe that massive and largely unregulated use of antibiotics in agriculture and aquaculture may present a great risk to the aquatic environment and human health.

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